Acacian Schism

The Acacian Schism (484-519) was a 35-year period of controversy between the western (Catholicism) church and the eastern (Miaphysitism) church that had its roots in the 451 AD Council of Chalcedon, where Pope Leo I declared that Jesus had two distinct aspects: godhood and manhood, and declared that the See of Rome had authority over the See of Constantinople. The schism ended in 519 when Ecumenical Patriarch John II and Emperor Justin I of Byzantium agreed to end the rivalry.

History
Nestorian Christianity was a major sect of Christianity that divided from the main church, and it stated that Jesus had both divine and human natures. There was controversy within Christianity over when to celebrate Christian Passover and Easter before that caused some heretic movements to rise up, but it was this issue that threatened to divide the eastern and western churches. In 451 AD, Pope Leo I hosted the Council of Chalcedon, where he condemned Nestorianism, although the "Chalcedonian Definition" stated that Jesus had both a divine and human nature, which was tantamount to Nestorianism. The council led to a divide between Miaphysitism, the eastern churches that followed Cyril of Alexandria in his fight against the hypocritical western church, which became Catholicism. The west and east broke contact as the Ostrogothic popes and the Byzantine ecumenical patriarchs had disputes.

Hoping to end the schism, Emperor Zeno of Byzantium issued the Henotikon in 482 AD, which endorsed the condemnations of the Nestorian founder Nestorius and the Eutychianism founder Eutyches that were issued at Chalcedon, but avoided any statement on Christ's natures. Both sides were angry at the Emperor getting involved in Church affairs, but the patriarchs of Antioch and Alexandria subscribed to the Henotikon. Emperor Anastasius I of Byzantium, the successor of Zeno on his death in 491 AD, adopted the Henotikon out of his sympathy towards the Miaphysites, and he refused to acknowledge the Catholic Church's excommunication of Acacius of Constantinople, who advised Zeno to pass the Henotikon. In 518, Anastasius died and Justin I of Byzantium, his successor, reunited the churches on 24 March 519, ending the schism.